Synephrine is a stimulant found naturally in bitter orange (Citrus aurantium). Its chemical structure resembles ephedrine, but it is less potent. Supplement makers include it in pre-workout and weight-loss products to promote alertness and energy.
Most people take synephrine for a short-term lift in energy and focus before exercise. The evidence for meaningful thermogenic or metabolism-boosting effects is weak and mixed. A typical routine uses it inside a pre-workout blend about 30 to 60 minutes before activity.
Synephrine can raise blood pressure and heart rate, a risk that climbs when you stack it with caffeine or other stimulants. Skip it if you have a cardiovascular condition, high blood pressure, or are pregnant or breastfeeding. Drug interactions lack thorough documentation, but use extra caution with blood-pressure medicines and other adrenergic agents.